Marine diesel engines such as a cross-head engine are typically lubricated with two different lubricants i.e., the first lubricant is for a cylinder liner and the second for a crankcase. The cylinder liner is typically lubricated with a cylinder oil (may be referred to as a MDCL), and the crankcase is lubricated by a system oil.
The cylinder oil, lubricates the inner walls of the engine cylinder and the piston ring pack. The lubricants are known to be used to assist in controlling corrosive and abrasive wear. The wear may be caused by unneutralised combustion products such as acids (typically sulphuric acid) being produced during combustion. Typically lubricants for MDCL have had a TBN of 40-50, or 70-100 mg KOH/g. There has been a trend for reduction in emissions (typically reduction of NOx formation, SOx formation) and a reduction in sulphated ash in engine oil lubricants.
US 2012/0214719 discloses a lubricating composition at least comprising: a base oil; and a detergent; wherein the detergent comprises at least 30 mol %, based on the total amount of detergent, of a sulphonate detergent having a BN (Base Number) of from 0.1 to 80 mg KOH/g; wherein the detergent comprises from 30 to 70 mol %, based on the total amount of detergent, of a phenate detergent; wherein the lubricating composition comprises at least 4 wt. % of detergent, based on the total weight of the composition; and wherein the lubricating composition has a TBN (total base number) (according to ASTM D 2896) of at least 10 mg KOH/g. The engine disclosed are slow- and medium-speed marine and stationary diesel engines that operate at high pressures, high temperatures and long-strokes. The problem disclosed is to improve deposit formation control properties.
CA 2818240 discloses a two-stroke, cross-head, slow-speed, compression-ignited marine engine is operated by: (i) fuelling it with a diesel fuel, as a pilot fuel, and with a low sulphur fuel, as a main fuel; and (ii) lubricating the engine cylinder(s) with a lubricant having a BN of 20 or less and having a detergent additive system comprising at least two different metal detergents each having one surfactant group selected from phenate, salicylate and sulphonate, or one or more complex metal detergents containing two or more different surfactant soap groups selected from phenate, salicylate and sulphonate. The sulphonate detergent disclosed in a dependent claim has a total base number (TBN) as determined by ASTM D 2896-98 of greater than 100.
CA 2813538 discloses a two-stroke, cross-head, slow-speed, compression-ignited marine engine is operated by: (i) fuelling it with a diesel fuel, as a pilot fuel, and with a low sulphur fuel, as a main fuel; and (ii) lubricating the engine cylinder(s) with a lubricant having a BN of 20 or less and having a detergent additive system comprising one or more different metal detergents having a surfactant group selected from phenate, salicylate and sulphonate, or one or more complex metal detergents containing two or more different surfactant soap groups selected from phenate, salicylate and sulphonate, and a distilled cashew nut shell liquid or hydrogenated distilled cashew nut shell liquid. A dependent claim describes the cylinder lubricant having a base number (BN) of 15 or less, preferably 5 to 15, or more preferably 10 to 15.
WO2013/119623 discloses sulphurized alkaline earth metal (e.g., calcium) dodecylphenate is prepared by reacting (i) dodecylphenol with (ii) calcium hydroxide or calcium oxide in an amount of about 0.3 to about 0.7 moles per mole of dodecylphenol charged and (iii) an alkylene glycol in an amount of about 0.13 to about 0.6 moles per mole of dodecylphenol charged; and reacting the product of the first step with sulphur in an amount of about 1.6 to about 3 moles per mole of dodecylphenol charged; and thereafter optionally reacting the product with additional calcium hydroxide or calcium oxide and with carbon dioxide so as to form an overbased phenate.
U.S. Pat. No. 6,429,179 discloses a calcium overbased detergent which is substantially free from inorganic halides and ammonium salts, formed by treating with an overbasing agent, a mixture containing at least one basic calcium compound and a surfactant system comprising at least two surfactants, at least one of which is a sulphurized or non-sulphurized phenol and at least one other of which is a surfactant other than a phenol surfactant, the proportion of the said phenol in the surfactant system being at least 45 mass % and the overbased detergent having a TBN: % surfactant ratio of at least 14. The calcium overbased detergent is useful for MDCL engines.